1. Field of the Invention
The present invention relates to valves disposed to prevent entry of liquid into a conduit connected as a vent to a receptacle or vault, and to a receptacle or vault provided with such a valve. The valve enables gases to flow in both direction within the conduit to bring equilibrium to ambient pressures, but prevents flooding of the receptacle or vault.
2. Description of the Prior Art
Electrical equipment is frequently stored in enclosures such as cabinets or vaults so that the equipment is located proximate premises served by the equipment, while enabling the equipment to remain substantially inaccessible to the public. In particular, telephone utility companies store batteries for operating the telephone system. Cabinets and vaults are useful in protecting batteries against animals and human vandals and thieves, but are prone to deleterious influences shortening battery life.
The useful life of batteries is reduced by exposure to elevated temperatures and to water. Battery manufacturers supplying batteries typically specify that the environment of the battery average no higher than 77.degree. F. over time and not to exceed 92.degree. F. at any time. Therefore, it is desirable to limit temperatures within and to deny infiltration of water into any enclosure housing batteries. Water may infiltrate due to flooding resulting from flooding waterways and temporary high water tables.
Water vapor will condense when temperatures cool, and will come to rest on battery surfaces, ceiling surfaces above the batteries, and on battery racks, with eventual drippage onto the batteries. Operation of acid using batteries typically releases hydrogen into the air due to electrolysis of water from the acid. Hydrogen is notoriously combustible, and must be vented to mitigate hazards of fire and explosions. Therefore, it is not feasible to fully seal the enclosure to eliminate infiltration by water. Simultaneously, the enclosure must limit its internal temperature.
Underground vaults for protecting electrical equipment are notoriously old. Representative underground vaults are shown in U.S. Pat. Nos. 3,390,225, issued to Robert O. Couch et al. on Jun. 25, 1968, 3,420,943, issued to Herbert D. Short on Jan. 7, 1969, and 4,709,120, issued to Dean C. Pearson on Nov. 24, 1987, as well as in my prior application identified above.
Vaults may be fully covered by the earth, or may be partially exposed above grade. In either case, they are susceptible to flooding if provided with a vent. A suitable valve is needed to enable air to flow both into the vault from outside, and from the vault to purge oxygen and hydrogen which may evolve from electrolysis of battery fluids, and to purge gases employed to flush the atmosphere of the vault. To properly protect batteries and other sensitive apparatus contained within the vault, the valve must prevent rising water from entering the vault through the vent.
The prior art has proposed venting valves which close under certain specified conditions. U.S. Pat. Nos. 4,487,215, issued to Charles J. Green on Dec. 11, 1994, and 5,042,519, issued to James R. Kerlin on Aug. 27, 1991, both describe fuel tank vent valves having two balls disposed to obstruct flow under certain conditions. However, the lower of the two vertically arrayed balls in both prior art patents are made from materials denser than the liquid they control. By contrast, the two balls of the novel valve are floats. The aforementioned prior art valves would entirely fail to operate as does the novel valve, wherein the lower ball floats, thereby exerting buoyant force acting on the upper ball when liquid enters the valve housing.
U.S. Pat. No. 4,524,794, issued to Frederick K. Haines on Jun. 25, 1985, shows a valve having two vertically arrayed balls. However, in Haines, the balls are obstructed with contact with one another. Also, the lower ball is fixed to a pivotally mounted lever which unseats the lower ball responsive to horizontal flow beneath the valve housing. In the present invention, both balls are free to move about within a common chamber, and normally contact one another both when air flows through the valve housing and also when liquid enters the valve housing. Also the valve housing of Haines opens upwardly to the atmosphere. Such a feature would defeat operation in the present invention.
U.S. Pat. No. 4,457,325, issued to Charles J. Green on Jul. 3, 1984, describes a fuel vent valve having three balls. However, the subject valve of Green has construction radically differing from that of the present invention. Whereas the novel valve has two float balls constrained to move within a limited portion of a conduit associated with the valve, the device of Green includes a valve housing containing two of the three valves. This valve housing is spring biased downwardly. By contrast, there is no spring in the present invention. In Green, none of the balls are themselves valves. Of the two balls in the valve housing in Green, one is of relatively great density, unlike the present invention. Also, the valve of Green has a seal which closes the valve housing regardless of valve position. This seal releases gases responsively to attainment of a predetermined high temperature. The novel valve is always open, and has no second closure corresponding to the seal of Green.
U.S. Pat. Nos. 4,630,531, issued to Werner Krauss on Dec. 23, 1986, and 5,115,830, issued to Bo Harde on May 26, 1992, both illustrate single ball type valves. The present invention has two balls which act in tandem, producing closing acting far more effective than would be provided by only one ball. The valve of Krauss incorporates elements of an associated pneumatic system absent and unnecessary in the present invention. In Harde, the ball is not itself a valve. Instead, it assists the valve in closing under conditions of severe inclination and inversion of the entire device. In the present invention, one of the balls is a valve, and the novel valve apparatus can close the conduit with its associated apparatus in the upright position.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.